// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2008-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
// Copyright (C) 2006-2008 Benoit Jacob <jacob.benoit.1@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_VECTORBLOCK_H
#define EIGEN_VECTORBLOCK_H

namespace Eigen {

namespace internal {
template<typename VectorType, int Size>
struct traits<VectorBlock<VectorType, Size>>
	: public traits<Block<VectorType,
						  traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
						  traits<VectorType>::Flags & RowMajorBit ? Size : 1>>
{};
}

/** \class VectorBlock
 * \ingroup Core_Module
 *
 * \brief Expression of a fixed-size or dynamic-size sub-vector
 *
 * \tparam VectorType the type of the object in which we are taking a sub-vector
 * \tparam Size size of the sub-vector we are taking at compile time (optional)
 *
 * This class represents an expression of either a fixed-size or dynamic-size sub-vector.
 * It is the return type of DenseBase::segment(Index,Index) and DenseBase::segment<int>(Index) and
 * most of the time this is the only way it is used.
 *
 * However, if you want to directly manipulate sub-vector expressions,
 * for instance if you want to write a function returning such an expression, you
 * will need to use this class.
 *
 * Here is an example illustrating the dynamic case:
 * \include class_VectorBlock.cpp
 * Output: \verbinclude class_VectorBlock.out
 *
 * \note Even though this expression has dynamic size, in the case where \a VectorType
 * has fixed size, this expression inherits a fixed maximal size which means that evaluating
 * it does not cause a dynamic memory allocation.
 *
 * Here is an example illustrating the fixed-size case:
 * \include class_FixedVectorBlock.cpp
 * Output: \verbinclude class_FixedVectorBlock.out
 *
 * \sa class Block, DenseBase::segment(Index,Index,Index,Index), DenseBase::segment(Index,Index)
 */
template<typename VectorType, int Size>
class VectorBlock
	: public Block<VectorType,
				   internal::traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
				   internal::traits<VectorType>::Flags & RowMajorBit ? Size : 1>
{
	typedef Block<VectorType,
				  internal::traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
				  internal::traits<VectorType>::Flags & RowMajorBit ? Size : 1>
		Base;
	enum
	{
		IsColVector = !(internal::traits<VectorType>::Flags & RowMajorBit)
	};

  public:
	EIGEN_DENSE_PUBLIC_INTERFACE(VectorBlock)

	using Base::operator=;

	/** Dynamic-size constructor
	 */
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE VectorBlock(VectorType& vector, Index start, Index size)
		: Base(vector, IsColVector ? start : 0, IsColVector ? 0 : start, IsColVector ? size : 1, IsColVector ? 1 : size)
	{
		EIGEN_STATIC_ASSERT_VECTOR_ONLY(VectorBlock);
	}

	/** Fixed-size constructor
	 */
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE VectorBlock(VectorType& vector, Index start)
		: Base(vector, IsColVector ? start : 0, IsColVector ? 0 : start)
	{
		EIGEN_STATIC_ASSERT_VECTOR_ONLY(VectorBlock);
	}
};

} // end namespace Eigen

#endif // EIGEN_VECTORBLOCK_H
